While the turtles are fighting the foot clan and Shredder down in the sewers, the Kraang manage to abduct all the people on the surface of New York. The turtles then have to find how to get all the humans back.

With this, any OC or non-foot/turtle characters could just have somehow evaded abduction. And it's up to Shredder if they're going to help or not, or try to end Splinter.

I figure this would be the nick verse, but we could use any and just sub out the kraang for someone else